The Messenger of Allah ﷺ said, "Whoever says one hundred times in a day, 'There is no god but Allah alone, with no partner. To Him belongs the dominion, to Him belongs all praise, and He has power over all things,' it will be equivalent to freeing ten slaves, one hundred good deeds will be recorded for him, one hundred sins will be erased from him, and it will be a protection for him from Satan throughout that day until evening. No one will come with anything better than what he has brought, except someone who has done more than that."
أن رسول الله ﷺ قال: من قال لا إله إلا الله وحده لا شريك له، له الملك وله الحمد وهو على كل شيء قدير في يوم مائة مرة كانت له عدل عشر رقاب، وكتبت له مائة حسنة، ومحيت عنه مائة سيئة، وكانت له حرزا من الشيطان يومه ذلك حتى يمسي، ولم يأت أحد بأفضل مما جاء به إلا أحد عمل أكثر من ذلك.
Malik narrated it in the Book of the Quran (20), from Sumayy, the freedman of Abu Bakr, from Abu Salih Samman, from Abu Hurairah, who related it.Bukhari narrated it in the Book of Supplications (6403), and Muslim in the Book of Remembrance and Supplication (2691), both of them through the route of Malik, with the same wording.